Composite slab for hot tops



Mach 2, 1965 F. J. INGALA 3,171,173

COMPOSITE SLAB FOR HOT TOPS I Filed May 4, 1962 INVENTOR. 6194M? 4/A1044 United States Patent 3,171,173 COMPGSITE SLABFOR HGT TOPS Frank J.Ingala, 3323 W. 64th Place, hicago, Ill. Filed May 4, I962, Ser. No.192,464 2' Claims. (Cl. 2214'i) The present invention relates to a heatinsulating me dium, particularly designed for hot top molds, and to amethod of making the same.

When molten metal is poured into a mold, the first metal that freezesagainst the mold wall shrinks slowly and this shrinkage is immediatelyfilled by the molten metal in contact with it. Each succeeding layerfreezing parallel to the mold surfaces shrinks similarly and takesmolten metal from the center. The molten pool in the center graduallysinks downward as it feeds the shrinking walls. This continues as longas the chilling effect of the mold wall is felt in the molten pool. Whenthis effect is no'lo'nger felt, the molten metal freezes slowlythroughout and shrinks downward. The net result is a casting with soundwall, and with an axial cavity or pipe, extending a considerabledistance downward.

In plants making killed steel, a hot top is placed on the top of themold to control the depth of the pipe. In small ingot practice these hottops usually take the form of life clay shells, which are heated as muchas possible before being placed on the molds. In large ingot practicehot tops may be sectional pieces of fire clay, brick, or even linedsteel castings, and the preheating is not so important because of thevolume of hot metal they will contain. These hot tops are smaller insection than the mold, and are shiinnied up above the mold top so thatthey can float on the metal in the filled mold, thus giving ample spacefor shrinkage to take place without binding the hot top to the top ofthe mold. If such binding should occur on various types of high carbonalloy, and high speed steel, ruptured ingots might result. The spacethus exposed between the mold and the hot top may be sealed with wetsand to prevent leakage as the metal rises in the hot top, or leakagemay be prevented by delaying the pouring for a'short time at the joint.The volume of the hot top, depending upon the type of steel, may varyfrom about ten' to eighte'en'percent.

While many hot top systems have been proposed in the past, they have notalways proved to be satisfactory for various reasons. The provision-of amore completely satisfactory composition for this purpose is theprincipal object of the present invention.

A further object of the invention is to provide an economical laminatedcomposition for hot tops.

A further object of theinvention is to provide a method for themanufacture of compositions particularly suited for use in hot topmolds.

In'general, the present invention provides a heat insulatiori medium forhot top walls which includes a laminate having a base containing amineral insulating material, a centrally disposed block secured to thebase and also containing a mineral insulating material, together withlayers of a combination of smolderable vegetable material, andcombustible metal'particles disposed on both sides of the block, withthe layers, the block, andthe base being bonded together intoaself-sustaining structure. With the arrangement described, I am able tocontrol the cooling characteristics of the ingot more carefully with theresult that the outer periphery of the casting does not solidifyprematurely and thereby cause excessive shrinkage of the castingresulting in excessive pipe formation. With the preferred embodiment ofthe present invention, I can generate high temperatures of the order of2200 F. in selected areas of the hot top, for periods of about ninetyminutes so that a substantially uniformly cooled casting results.

The mineral insulating material of which the base and the block arepreferably composed contains a mineral insulating material such asasbestos, together with combustible fibers and a resinous binder. Thistype of composition is specifically disclosed and claimed in mycopending application Serial No. 95, 483, filed Mar. 14, 1961, nowabandoned. As disclosed in that application, a preferred binder has thefollowing composition:

Table I Ingredient Particle size Percent by weight Vegetable starch (cg.potatoes 200 to-400mesh -60 or corn starch). 7 Soy bean flour 200 to 250mesh 10-30 Wood rosin 150 to 400 mesh 15-35 Bituminous material (e.g.150 to 400 mesh 10-20 powdered pitch).

Table II Ingredient Range Preferred,

percent Asbestos -65% by wcight 55 Combustible fibers 20-40% Granulatedrosin to 240% 5 mesh, M.P. -180" 0.). a

The binder and the dry ingredients are mixed in a clay mixer until themass assumes a homogenous consistency. The mud-like mass thus producedis then poured into a form and pressed to a self-sustaining compact;Finally, the compact is removed from the form and dried in aii oven at200 F. for about two hours.

The'compact which results consists of the combustible fibers, suchaspaper, horsehair, of the like, uniformly dispersed throughout theasbestos and the various binding agents. The compact has" an excellentheat retaining property. As the combustible fibers burn in the compact,the heat is retained in the mass. v

The smolderabl'e vegetable material which is used in the course of thepresent invention is preferably composed of crushed olive stones,normally measuring from about to inch in maximum dimension.Alternatively, material such as walnut shells or the like can beemployed, but I have fourid that olive stones possess sub stantiallybetter properties for this use than other types of vegetablematter.

The hot top composition also includes" particles of a combustible metalof which aluminum is the preferred example, although zinc can also beused For the purposes of this invention, it is desirable to keep" theparticle size of the combustible metal in the range'from about 12" meshto about 30 mesh. I

Together with the combustible metal, I prefer to add a diluent such as acompletely oxidized material which tempers the oxidation of the metaland thereby prevents the build up of excessive and uncontrolled amountsof heat. For this purpose, I prefer to use ferric oxide having aparticle size of about 300 mesh.

I11 general, the relative proportions of the ingredients will lie withinthe following ranges:

A further description of the present invention will be made inconjunction with the attached sheet of drawings, which illustrate thepreferred embodiment thereof.

In the drawings:

FIGURE 1 is a view in elevation of the base;

FIGURE 2 is a view in elevation illustrating the manner in which thecentrally disposed block is formed over the base;

FIGURE 3 is a view illustrating the manner in which the layers ofvegetable material, combustible metal, and diluent are arranged aboutthe centrally disposed block;

FIGURE 4 is a fragmentary view illustrating the manner in which thelaminated structure is compressed and consolidated by heating; and

FIGURE 5 is a fragmentary view in perspective of the finished hot topmold composition.

As shown in the drawings:

In FIGURE 1, reference numeral indicates generally the base which isemployed for the hot top composition. As mentioned previously, the base10 preferably includes a mixture of asbestos fibers and the like,together with suitable binding agents and combustible fibers. The base10 is self-sustaining by virtue of the action of the binders and theheat supplied to the composition in its formation, all of which isdiscussed in a preceding portion of this specification.

In [the form of the invention shown in the drawings, a centrallydisposed block 11 (FIGURE 3) is provided over the base 10 by depositinga moldable mass 12 over the base and then applying pressure by means ofa forming plate 13. The mass 12 is preferably of the same composition asthe base 10, that is, contains a mixture of asbestos, combustiblefibers, and a resinous binder which preferably includes granulatedrosin, a bituminous material such as pitch and vegetable flour. Aftermolding the mass 12 into the configuration of the block 11, a layer ofolive stones 14 is disposed over the base on both sides of the centrallydisposed block 11. Then, a layer of a mixture of aluminum and ferricoxide, indicated at numeral 16 is disposed over the layer of olivestones 14. The aluminum or other metal should be thoroughly mixed withthe diluent in order to modify the burning properties of.the combustiblemetal sufficiently for the purposes of this invention. Finally, anadditional insulating layer 17 composed preferably of the same materialas contained in the block 11 and the base 10 is applied over the layer16 containing the combustible metal and the diluent. After thislaminated structure tis built up, a ram 18 is brought down on thesurface of the mass to consolidate it further, whereupon the pressedmass is subjected to a temperature of about 400 F. in a steam oven for aperiod of time of about one and a half hours. Under these conditions,the binders present in the block 11 and the insulating layer 17 aresoftened and diffuse through the layers to form a self-sustainingstructure when the heat is removed.

As illustrated in FIGURE 5, the composite hot top composition of thepresent invention has several areas of varying heat transfercharacteristics. The central area, represented by the block 11 isessentially a heat insulator although some heat is generated therein bythe combustion of the combustible fibers, when they are used in thecomposition of the base 10 and in the block 11. The areas on both sidesof the block 11 are essentially heat generating areas by virtue of thepresence of the combustible metal particles and the smolderable olivestones 14, as well as the combustible fibers which are disposed in thebase and in the overlying insulating layer 17. With this combination,the areas of the ingot outwardly from the center are kept hot forsubstantial periods of time so that premature chilling and the resultantformationof pipe is minimized.

The following specific example points out the manner in which theimproved structure of the present invention is manufactured.

In producing a block measuring 13 inches by 13 inches by 2 inches, abase measuring about /2 inch thick and composed of asbestos mixed with aresinous binder is employed. The block 11 is then molded to provide afinal thickness of about 2 inches. For this type of structure, aboutfour pounds of crushed olive stones, 1 and /2 pounds of aluminum pigmentpowder, and /2 pound of ferric oxide are employed. The aluminumparticles and the ferric oxide are premixed before application over thelayer of olive stones. After pressing and heating, as above described,it is advisable to dust some Portland cement over the top of thelaminated structure and wet trowel over the surface to serve as anadditional heat retainer.

It should be evident that various modifications can be made of thedescribed embodiment without departing from the scope of the presentinvention.

1 claim as my invention:

1. A heat insulating medium for hot top molds consisting of a laminateincluding a base and a centrally disposed block of lesser width securedto said base, both said base and said block consisting essentially of abinder containing from 30 to 60% by weight vegetable starch, 10 to 30%by weight soy bean flour, 15 to 35% wood rosin, and 10 to 20% powderedbituminous material, in combination with a mixture of 35 to 65% byweight asbestos, 20 to 40% by weight of combustible fibers and 2 to 10%by weight rosin, and alternating layers consisting essentially ofcrushed olive stones and aluminum particles disposed on both sides ofsaid block, said base, said block, and said layers being bonded togetherinto a selfsustaining structure, said olive stones constituting from 10to 40% by weight of the final product and said aluminum particlesconstituting from 5 to 25% by weight of the final product.

2. The heat insulating medium of claim 1 which also includes a ferricoxide diluent in admixture with said aluminum particles in an amount offrom 3 to 18% by weight of the final product.

References Cited by the Examiner UNITED STATES PATENTS 1,819,364 8/31Firth 22147 2,462,256 2/49 Charman et al 22--147 2,791,816 5/57 Pletschet a1. 22147 2,925,637 2/60 Edmonds et a1 22-147 FOREIGN PATENTS 828,1902/ 60 Great Britain. 868,599 5/61 Great Britain.

MICHAEL V. BRINDISI, Primary Examiner.

MARCUS U. LYONS, Examiner,

1. A HEAT INSULATING MEDIUM FOR HOT TOP MOLDS CONSISTING OF A LAMINATEINCLUDING A BASE AND A CENTRALLY DISPOSED BLOCK OF LESSER WIDTH SECUREDTO SAID BASE, BOTH SAID BASE AND SAID BLOCK CONSISTING ESSENTIALLY OF ABINDER CONTAINING FROM 30 TO 60% BY WEIGHT VEGETABLE STARCH, 10 TO 30%BY WEIGHT SOY BEAN FLOUR, 15 TO 35% WOOD ROSIN, AND 10 TO 20% POWDEREDBITUMINOUS MATERIAL, IN COMBINATION WITH A MIXTURE OF 35 TO 65% BYWEIGHT ASBESTOS, 20 TO 40% BY WEIGHT OF COMBUSTIBLE FIBERS AND 2 TO 10%BY WEIGHT ROSIN, AND ALTERNATING LAYERS CONSISTING ESSENTIALLY OFCRUSHED OLIVE STONES AND ALUMINUM PARTICLES DISPOSED ON BOTH SIDES OFSAID BLOCK, SAID BASE, SAID BLOCK, AND SAID LAYERS BEING BONDED TOGETHERINTO A SELFSUSTAINING STRUCTURE, SAID OLIVE STONES CONSTITUTING FROM 10TO 40% BY WEIGHT OF THE FINAL PRODUCT AND SAID ALUMINUM PARTICLESCONSTITUTING FROM 5 TO 25% BY WEIGHT OF THE FINAL PRODUCT.